Heavy-ion collisions

Altogether, we thus see a striking similarity, up to details, between the nuclear and the cluster responses for this clean Coulomb excitation mechanism with the prominent feature that the resonance modes turn out to represent robust, harmonic oscillations. It remains to be seen to what extent this behavior persists in other experimental situations. In the following we focus on heavy-ion collisions and laser-cluster interactions as complementary and widely studied excitation mechanisms. 

As seen above, the destruction of the resonance in the case of heavy-ion collisions is due to the coupling between surface and resonance modes. The cluster analog of nuclear surface vibrations is ionic motion. But this takes place at a much slower pace and cannot interfere dynamically with the electronic resonances. The plasmon is thus more robust against varying excitation mechanisms. There remains, however, the static aspect of the enormous surface distortions during nuclear fusion. Such a distortion could also be produced in the analogous process of cluster fission. And, indeed, it has been found that there is a chance to dissolve the plasmon into a broad, fragmented spectrum 

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The equation of state (EOS), the composition and the possible occurrence of phase transitions in nuclear matter are widely discussed topics not only in nuclear theory, but are also of great interest in astrophysics and cosmology. Experiments on heavy ion collisions, performed over the last decades, gave new insight into the behavior of nuclear systems in a broad range of densities and temperatures. The observed cluster abundances, their spectral distribution... 

As physics advances, its frontier has expanded. One of the frontiers under active exploration is matter at extreme conditions. Recent surprising data, obtained from heavy-ion collisions and compact stars such as neutron stars, and also some theoretical breakthroughs have stimulated active investigation in this field [1],... 

In reality, we are more interested in the intermediate density region, where the color superconducting phase may exist in the interior of neutron stars or may be created in heavy ion collisions. Unfortunately, we have little knowledge about this region we are not sure how the deconfinement and the chiral restoration phase transitions happen, how the QCD coupling constant evolves and how the strange quark behaves in dense matter, etc. Primarily, our current... 

If a macroscopic chunk of quark matter is created in heavy ion collisions or exists inside the compact stars, it must be in color singlet. So in the following discussions, color charge neutrality condition is always satisfied. 

Nowadays it is widely accepted that there should be realized various phases of QCD in temperature (T) - density (ftp,) plane. When we emphasize the low T and high pp region, the subjects are sometimes called physics of high-density QCD. The main purposes in this field should be to figure out the properties of phase transitions and new phases, and to extract their symmetry breaking pattern and low-energy excitation modes there on the basis of QCD. On the other hand, these studies have phenomenological implications on relativistic heavy-ion collisions and compact stars like neutron stars or quark stars. 

Anomalous behavior of fluctuations might manifest itself in the event-by-event analysis of the heavy ion collision data. In small (L) size systems, L < , (zero dimension case would be L order parameter to the specific heat is still increased, as we have mentioned, see [15]. The anomalous behavior of the specific heat may affect the heat transport. Also kinetic coefficients are substantially affected by fluctuations due to the shortening of the particle mean free paths, as the consequence of... 

Figure 5. Phase diagram for Nj =2 quark matter in the NCQM. The critical temperature for color superconductivity (2SC phase) can be high enough for this phase to reach close to the tricritical point which shall be explored in future heavy-ion collision experiments.

Since the discovery of the parton substructure of nucleons and its interpretation within the constituent quark model, much effort has been spent to explain the properties of these particles and the structure of high density phases of matter is under current experimental investigation in heavy-ion collisions [17]. While the diagnostics of a phase transition in experiments with heavy-ion beams faces the problems of strong non-equilibrium and finite size, the dense matter in a compact star forms a macroscopic system in thermal and chemical equilibrium for which effects signalling a phase transition shall be most pronounced [8],... 

As known from nuclear physics, a direct extension of quantal mean-field is delicate [36]. Fortunately enough, in the high excitation regime, where semi-classical approximations are likely to become acceptable, Boltzmann-like kinetic equations, offer an efficient alternative. They thus have been extensively used in nuclear physics for describing heavy-ion collisions (VUU,... 

Figure 2. Distribution of the sum of coincident electron and positron kinetic energies in heavy ion collisions at G.S.X. (ref. 15)...

The G. S. I. group measured the sum of the kinetic energies of electron-positron pairs produced in heavy ion collisions at GeV energies. The remarkable feature of these experiments was a sharp peak in the energy distribution, summed over the e+e pair (Fig. 2). This lead to speculation as to the origin of this mysterious peak. A large number of papers have been written on the subject. [15]... 

Norenberg, W. and Weidenmiiller, H.A. (1976). Introduction to the Theory of Heavy-Ion Collisions (Springer, Berlin). 

This summary of applications from chemical calculations to heavy-ion collision physics shows that DV-Xa calculations are an important tool in all of these fields and thus shows the usefulness of this method. 

P. E. Hodgson, Nuclear Heavy Ion Reactions, Clarendon Press, Oxford, 1978 W. U. Schroder, J. R. Huizenga, Damped Heavy Ion Collisions, Annu. Rev. Nucl. Sci. 27, 465 (1977)... 

R. Bock (Ed.), Heavy Ion Collisions, 3 Vols., North-Holland, Amsterdam, 1979-1981 D. A. Bromley (Ed.), Treatise on Heavy Ion Science, Vol. 4, Plenum Press, New York, 1985 R. Bock, G. Herrmaim, G. Siegbert, Schwetionenforschung, Wiss. Buchges., Darmstadt, 1993 J. V. Kratz, Radiochemical Studies of Complex Nuclear Reactions, Radiochim. Acta 70/71, 147 (1995)... 

Theoretical and experimental investigations of relativistic and QED effects in atomic physics and chemistry have increased continuously during the last decade. As a consequence of this interest in various relativistic phenomena and in their empirical manifestations a diverse field of research has developed linking together widespread activities ranging from high-energy heavy-ion collision physics, atomic or molecular physics and chemistry of heavy elements to solid-state physics. 

Electron-Positron Pair Creation in Relativistic Heavy-Ion Collisions... 

As we have mentioned above it is possible to evaluate the electromagnetic lepton pair production in the limiting case of infinite Lorentz factors y. One interesting aspect among others is that peripheral heavy-ion collisions at ultrarelativistic energies offer... 

Soff, G. (1980) Electron-positron pair creation and K-shell ionisation in relativistic heavy ion collisions. In Proc. XVIII Winter School, Selected Topics in Nuclear Structure, Bielsko-Biala, Polen, p. 201. 

Tho critical baryon density corresponds to pmax = 0. This leads to the ( (juations Uv + Us = G or Uv — Us — 2Mg = 0 or both. The first condition Uv + Us = 0 is fulfilled earlier than the second one. When the first condition is reached the nucleus becomes unbound, i.e., unstable with respect to emission of nucleons. So it is impossible to compress the nucleus more than the critical density in a self-consistent manner such densities should occur only as shortlived intermediate stages in a heavy-ion collision. Wc performed a constraint calculation with the monopole moment [23, 24, 25], which produced self-consistent solutions up to w 3po for the case of Pb. A chart for the critical densities of nuclear matter with different parameter sets is given in ref. [26]. We found that the critical densities are much larger for nuclear matter c ompared to finite nuclei in all available parameter sets. The TMl parameter set was chosen for our calculations, because it gives a larger critical density of about 3po ... 

In high energy heavy ion collisions it might be possible to produce antimatter clusters like d, He, etc. out of the highly correlated vacuum in contrast to their conventional production by fusing antibaryons, step by step, in phase space. 

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